Optimizing electrical field stimulation parameters reveals the maximum contractile function of human skeletal muscle...

Area of Science:

• Biomedical Engineering
• Tissue Engineering
• Regenerative Medicine

Background:

• Skeletal muscle microtissues are vital for developing therapies to restore muscle function.
• Standardized electrical field stimulation (EFS) parameters are lacking for assessing engineered muscle function.

Purpose of the Study:

• To establish a protocol for optimizing EFS parameters to elicit maximal contractile force in muscle microtissues.
• To identify key metrics for evaluating microtissue contractile function and kinetics.

Main Methods:

• Muscle microtissues were cultured on micropost platforms using various myoblast sources.
• EFS was applied, and microtissue contraction-induced micropost deflection was measured to quantify force.
• Pulse duration and frequency were systematically varied to determine optimal stimulation parameters.

Main Results:

• Optimal EFS pulse durations (20-80 ms) differed significantly from those used for native or previously engineered muscle.
• Peak tetanic force frequency varied by cell line (7-60 Hz), unlike native muscle (20-50 Hz).
• Muscle microtissues exhibited slower contraction and relaxation kinetics than native muscle, suggesting underdeveloped excitation-contraction coupling.

Conclusions:

• Failure to optimize EFS parameters can lead to underestimation of muscle microtissue functional capacity.
• Optimized EFS protocols and reporting of specific metrics are essential for advancing skeletal muscle therapies.
• Novel metrics like dynamic oscillation of force and duration-at-peak force offer insights into contraction kinetics.